As long as the gain of the amp is sufficient then passive preamp is a good option. It doesn't have to be in the same box as the power amp. Remember its the source component that drives the amp in such a case, CD players, DACs etc have high output levels, other sources may not.

I had read that somewhere, I take it I need to build more in the style of a gain card with the power supply boards close to the amp boards and the transformer in a separate box? I want to get this right first time because I cant afford to make mistakes with case size and layout.